This proposal concerns the magnetic circular dichroism (MCD) and absorption spectroscopy of porphyrins whose peripheral substituents (-CH double bond CH2, -COOH, -CHO, -COCH3, -CN), either alone or in concert, cause an inversion of the normal sign pattern in their MCD spectra. Our proposition is that the MCD and, concomitantly, the absorption spectrum of any substituted porphyrin or chlorin - regardless of the number, kind, or relative orientations of the substituents - can be predicted provided only that the MCD and absorption spectra of a fairly limited set of disubstituted porphyrins is known. We propose to synthesize the required sets of disubstituted porphyrins and to measure their spectra as free-bases and as complexed with a limited number of metal ions. We will use this data set in conjunction with some theoretical work to establish symmetry rules for predicting spectra. We will then test these predictions on an entirely different set of porphyrins.